Historic Nor’Easter NE US snow storm January 25-27

A “potentially historic and crippling snow storm” is imminent for the USA NE seaboard especially New York State with cities from New York to Boston being warned by weather agencies of a potentially life threatening blizzard lasting some 48 hours. Update Tues 27: whilst the worst of the blizzard missed New York heavy snow occurred further North. The system tracked further east than modelled.

New York escaped worst, but Boston hit as expected with record snow in New England

Potentially 36 inches (3 feet) of snow could fall in places (that’s waist deep!) as a Nor’Easter (NorthEasterly) wind buckles round a rapidly deepening low tracking NW up the coast over the next 48 hours. All weather agencies are busy getting the news out to people in the regions likely to be impacted.

Official warnings from NOAA and all regional weather agencies are giving these urban populations warning after the system has caught computer models napping. The storm has rather unexpectedly “blown up” recently to become a potential threat only in the last 24 hours or so.

The charts below show the synoptic set-up that develops this system, named Juno, currently a rather benign low tracking west out of continental US. This LOW is forecast to deepen rapidly due to it’s location in relation to a fast meridional jetstream looping round a HIGH pressure ridge in the US west. The LOW is dragging cold air from the continent interior and, as this cold air interacts with humid air and plenty of moisture over the Atlantic, it will turn into a snow-making machine that could last 48 hours and dump feet of snow widely across many places indicated on maps above.

synoptic analysis chart Sun 25 Jan 2015

meridional jetstream

anomaly chart 500hPa

sea level pressure

Here are some synoptic charts showing the development. Note the track sliding up the NE coast. The Nor’Easter wind itself can be seen developing on the northern edge of the low which, as it is forecast to slow and stall while it deepens (a common feature of bomb depressions) the strong NorthEasterly gales, some up to 70mph, will continue to pump snow across parts of the NE building up depths to 2 – 3 feet in places.

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Note the warm sea surface temperatures off shore which will provide enormous quantities of moisture for snow production on the NE wind.

Here is a chart showing minimum temperatures and possible snow cover by Wednesday.

minimum temps

snow cover mm

The US is more used to heavy snow and more able to cope with it than the UK because the USA has a continental climate which experiences colder winters with more regular and significant snow events. Earlier this winter Buffalo recorded feet of lake-effect snow. Even so, this snow storm is serious and a state of emergency has been issued for New York. The difference this time is that this storm will dump a lot of snow in a very short space of time and more people will be impacted in a densely populated and urbanised part of the USA.

The National Weather Service and regional weather agencies and the New York Mayor have all issued weather warnings for the blizzard urging people not to underestimate the possible impacts of 2-3 feet of snowfall over the next 48 hours.

Excellent write up and explanation of the evolution of this Nor’Easter storm http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2015/01/28/raging-snow-howling-wind-the-meteorological-evolution-of-the-blizzard-of-2015/